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ENV CHAPTER 11-1: WATER RESOURCES
There are 2 kinds of water: fresh and saltMost of the human uses (drinking and agriculture) require fresh It is a renewable resource b/c it is circulated in the water cycleWater cycle = continuous movement of water between earth and the atmosphere (evaporation, condensation, precipitation) Global water distribution-71% of earth is covered with water – 97% of it is saltwater- of the freshwater (3%) – 77% is frozen in glaciers and ice caps- most of what we use comes from rivers, lakes and a narrow zone beneath earth’s surface. Surface water = fresh water on earth’s land surfaceLakes, rivers, streams, wetlandsThrough history people have tended to concentrate around reliable sources of water Rivers start as streams from mountains, hills, and plains. - The streams hook up to form rivers- As streams and rivers move across the land they form a river system = flowing network of water. Examples include Mississippi, Amazon, Nile- Watershed = the area of land drained by a river. The Mississippi watershed covers half the US Groundwater = water stored under the earth’s surface in sediment and rock formationsCollects from rainwater that percolates through the groundWatertable = when the water reaches a point where the soil and rocks are saturatedIn wet areas the watertable is high, or at the surface. In desserts it could be hundreds of meters belowAquifer = underground formation where groundwater accumulates. Aquifers usually form in permeable rocks – soil or rocks that allow water to flow through itPermeable – gravel, limestone. Impermeable – clay, granite.Porosity = the amount of space between the rock particles. Water goes in the pores. Recharge zone = area of earth’s surface where water percolates down onto the aquifer.They are environmentally sensitive. Pollution can get into the water, or buildings on top can act as impermeable layers so the aquifer can’t recharge. If you dig deep enough you’ll eventually hit waterWell = hole dug to reach groundwaterENV CHAPTER 11-2: WATER USE AND MANAGEMENT
3 major uses for water:1. residentialmost water must be treated to make it safe to drink (potable)treatment removes poisonous elements (arsenic, mercury, lead) and pathogens (organisms that cause disease (bacteria, protozoa, worms)common methods include both physical and chemical treatment2. industrialwater is used to manufacture goods, dispose of waste, generate powermost is used to cool power plants3. agriculturalmost freshwater used worldwide is used to water cropsirrigation = providing plants with water other than from direct precipitationsprinklers, flooding, ditches and canals water management projects = altering the natural flow of water to make it more usefulgoals: bringing in water to make a dry area habitable creating a reservoir for drinking or recreation generating electric powerwater management projects have changed the American southwest diversion projects = all or part of a river can be diverted into canals that carry water very farexample: the Colorado river and the southwestdams = structure built across a river to control it’s flowreservoir = artificial lake formed behind a dam pros: drinking water, recreation, hydroelectric powercons: disrupting ecosystems, displacing people, dam failure water conservation – slow depletion of water sources to keep the price reasonableagriculture – most is lost due to evaporation during irrigation. Drip irrigation is an alternativeindustry – recycling cooling and wastewaterhome – don’t let the water run, shorter showers, water-saving toilets and shower heads, only wash full loads, water your lawn sparingly in some places water conservation is not enough – need to use desalination and transportdesalination = removing salt from saltwater (heating the water and collecting the vapor)transport = bringing in water from other regions
CHAPTER 11-3: WATER POLLUTION
Water pollution = introduction of chemical, physical or biological agents into water that degrade water quality and adversely affect the organisms that depend on it.two main causes: industrialization and human population growth pollution comes from two kinds of sources: point and nonpoint 1. point-source pollutionpollution discharged from a single source (factory, leaking tanker)it can often be identified and traced back to the source 2. nonpoint-source pollutioncomes from many different sources that are often hard to identify (runoff into a river from the surrounding watershed)since the pollution comes from different places, it’s hard to regulate and controlcontrol depends on public awareness. Most common water pollutants:1. pathogens – disease-causing organisms (from feces) – nonpoint2. organic matter – plant and animal matter remains – nonpoint3. organic chemicals – pesticides, fertilizers, plastics, detergents, petroleum productss – nonpoint4. inorganic chemicals – acids, bases, salts, industrial chemicals – point and nonpoint5. heavy metals – lead, mercury, arsenic – point and nonpoint6. physical agents – heat and suspended solids – point and nonpoint Wastewater = water that contains waste from homes or industry (what goes down the drain) It can be treated in plants so it’s safe enough to be returned to rivers and lakes- Most of the biodegradable material can be broken down by living organisms- sewage sludge = the solid material that remains after treatment- it can be incinerated, or used for fertilizer or mixed with clay and used for bricks Things we do to pollute:- artificial eutrophication = too many nutrients in a body of water- leads to algal blooms and suffocation of lakes- Thermal pollution = increase in the temperature of a body of water O2 in the water drops and organisms can die from suffocation or heat- groundwater pollution = pollution on the surface percolates into the groundwater groundwater pollution is hard to clean up b/c ground water recharges very slowly and b/c pollutants stick to the materials that make up an aquifer ocean pollutionmost comes from nonpoint sources on land (garbage, waste, sewage dumping)oil spils are another source water pollution and ecosystems- many pollutants accumulate b/c they do not decompose- biomagnification = accumulation of pollutants at successive levels of the food chain. Happens b/c each organism stores the pollutant in its body tissue, and as the trophic levels go up, the concentration of the pollutant does too. Laws to improve water quality1. 1972 clean water act – goal to make all surface water safe enough for fishing and swimming. Banned pollutant discharge, required removal of heavy metals.2. 1972 marine protection, research, and sanctuaries act – stricter laws against ocean dumping3. 1990 oil pollution act – requires double-hulled tankersGoogle Sites
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